1. Field of the Invention
The invention relates to a pickling machine comprising a plurality of hydraulically buffered needles that are arranged on a common carrier, valve means for controlling the supply of brine to the needles, and pressure cylinders associated with the needles for buffering the same.
2. Description of the Related Art
In such a pickling machine, the brine is injected under pressure into the items to be pickled by means of the needles. The items to be pickled are fed on a conveyer below the needles, and by lowering the carrier, the needles are forced into the items to be pickled. By means of the valve means, the supply of brine is so controlled that the brine in only discharged via the needles when the latter penetrate into the item to be pickled.
In most cases, the supply of brine to the needles is achieved via a brine chamber which is common to all the needles and is formed within the carrier. Then, a single valve blocking the flow of brine into the brine chamber is sufficed for controlling the supply of brine.
In certain cases, for example when pickling ham with bones, the needles should be buffered such that they are capable of retreating upwardly relative to the needle carrier, if they impinge onto a bone when the carrier is lowered. On the other hand, however, the needles must be biased downwardly with a force sufficient for causing the needles to penetrate into the item to be pickled. In principle, this may be achieved by forming, at each needle, a piston that is guided in a pressure cylinder. Then, the individual needles are connected to the brine chamber via their respective pressure cylinders, so that the piston is acted upon by the pressure of the brine. The active area of the piston is adapted to the pressure of the brine such that the force of the piston overcomes the resistance opposing to the penetration of the needle into the item to be pickled. If the needle hits a bone, the needle and the piston may retreat upwardly against the pressure of the brine.
This solution has the advantage that no mechanical components such as compression springs or the like are needed for buffering the needles, so that the construction of the machine can be simplified and cleaning of the machine can be facilitated. It is a drawback, however, that, if the needles are withdrawn from the item to be pickled and the supply valve has been closed, a relatively large amount of brine will still drop out of the needles. This leads to an increased consumption of brine and to a serious pollution of the working environment.
It is an object of the invention to provide a pickling machine of the type indicated above, in which the tendency of brine to drop out of the needles is suppressed.
According to the invention, this object is achieved by the features that the valve means comprise an individual valve for each needle and the pressure cylinders are arranged to be blocked individually by said valves.
Thus, when the valves have been closed, each individual needle communicates only with the relatively small volume of the associated pressure cylinder. When the needle is withdrawn from the item to be pickled and brine tends to leak out, a subatmospheric pressure will be built up in the pressure cylinder very rapidly and will suppress the leakage of brine. The pressure cylinder will not be vented because venting air could only enter through the needle itself which, however, is still filled with brine. By hydraulically separating the individual pressure cylinders from one another, it is avoided that air enters into the brine chamber through individual ones of the needles, and that an amount of brine, which corresponds to the volume of the air having entered, leaks out of other ones of the needles. In this way, the invention permits a very clean processing with smallest possible consumption of brine.
Preferably, the individual valves are constructed as tube valves that are arranged directly above the top ends of the pressure cylinders. Since all the valves lie in a common plane, it is possible to close all valves synchronously with a single squeeze grid, so that only a single control member is needed for controlling the plurality of valves, for example, a control member in the form of a tappet which moves the squeeze grid into the squeezing position. Thanks to the own elasticity of the tubing""s forming the individual tube valves, the squeeze grid will automatically be returned into the open position when the tappet is released. Thus, no additional return means are needed. Since the needles and the associated pressure cylinders as well as the associated tube valves are arranged on a common vertical axis, cleaning of the brine supply system of the machine is facilitated considerably.
Typically, a pickling machine has a pressing member which is guided to be movable in vertical direction relative to the needle carrier and which is pierced by the lower ends of the needles. This pressing member has the main purpose of wiping the item to be pickled off from the needles when the latter are withdrawn upwardly. It is known that the relative movements between the pressing member and the needle carrier can be utilized for controlling the supply of brine. In the machine according to the invention, this can be achieved in a particularly simple way by forming a cam on a member connected to the pressing member, which cam acts upon the tappet and thus closes all tube valves, when the pressing member is in its lower extreme position relative to the needles.
According to a useful further development of the invention, the cam may be shaped such that it opens and closes the individual tube valves gradually while the pressing member moves upwardly relative to the needles. In this way, the flow rate of brine through the individual needles and, hence, the amount of brine injected into the item to be pickled, can be controlled in a stroke-dependant way, so that it is possible for example, to inject a larger amount of brine into the core region of the item to be pickled than into the peripheral regions. The stroke dependency of the flow rate of brine may be specifically adapted to the item to be pickled by appropriately selecting the control contour on the cam. This function principle may advantageously be utilized also independently of the features described above and thus constitutes a separate aspect of the invention.
When the pressing member is in its lower extreme position and the tube valves are held closed by the cam, the needles can be moved upwardly relative to the carrier, because the brine which is then displaced out of the pressure cylinders can be drained through the needles. However, as soon as the pressing member is lifted and the tube valves are opened, the pistons of all needles are subjected to the pressure again, so that all needles return into their lower end position relative to the needle carrier.
If there is only a very little start-up time between the timing at which the tube valves open and the timing at which the needles actually penetrate into the item to be pickled, then it may happen however, that the needle, that had been lifted previously, will still lag relative to the other needles when penetrating into the item to be pickled. This effect, which may possibly be undesirable, may be avoided for example by providing, in each pressure cylinder, a compression spring which is preferably removable and which returns the piston and the needle into the lower end position even before the piston is exposed to pressure. As an alternative, it is possible to prevent already the needles from being lifted, by blocking the needles in their lower end position, when the pressing member is in the lower extreme position. This may be achieved by means of a fixing member latch or clamping member, which is actuated by a cam, similarly as the tappet of the valve means.